Unit Name: Mount Wilson Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: late Middle Ordovician (N.A.) - early Late Ordovician (N.A.) (460.9 - 455.8 ma)
Province/Territory: Alberta; British Columbia

Originator: Walcott, C.D., 1923; Norford. B.S., 1969.

Type Locality:
Mount Wilson, northeast of Saskatchewan River, Alberta, near 52 deg 00'N, 116 deg 45'W.

Distribution:
At the type section the formation is about 165 m (541 ft) thick (Norford, 1969). In the Beaverfoot Range, about 10 km (6.3 mi) south of Golden the formation is about 450 m (1,476 ft) thick (Evans, 1933); from there the formation thins southward to Bull River, southeastern British Columbia.

Lithology:
Light grey to white, thin- to thick-bedded and partly cross-stratified quartz sandstone, well-cemented by clear quartz.

Relationship:
The name Mount Wilson Formation has replaced the term Wonah Quartzite. Mount Wilson quartz sandstones lie conformably on the Owen Creek Formation (Middle Ordovician) in the eastern main ranges and on Glenogle Formation shales (Middle Ordovician: Caradocian) in the western ranges. Larson and Jackson (1966) suggested that a regional hiatus lies at the base of the Mount Wilson Formation, accounting for the absence of graptolite zones. Upper Ordovician (Ashgillian) beds of the Beaverfoot Formation regionally overstep the Mount Wilson strata. No diagnostic fossils have been recovered from the Mount Wilson Formation.

History:
Walcott erected the Mount Wilson Formation but did not examine the type section. North and Henderson (1954) suggested the name be applied to the succession of quartz sandstone then known as the Wonah Quartzite, occupying a homotaxial position in the western ranges. That suggestion has been followed in subsequent mapping (Norford, 1969; Price and Mountjoy, 1979).

Other Citations:
Evans, 1933; Larson and Jackson, 1966; Norford, 1969; North and Henderson, 1954; Price and Mountjoy, 1979; Walcott, 1923.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: H.R. Balkwill
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 27 May 2004